Biyoteknoloji/Makale Koleksiyonu

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https://hdl.handle.net/20.500.12395/15497

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Investigation of Optoelectronic Properties of Organic Semiconductor Tetracyaoquinodimethane Based Heterostructures
(Selçuk Üniversitesi Fen Fakültesi, 2021) Avcı, Burcu; Hussaini, Ali Akbar; Erdal, Mehmet Okan; Yıldırım, Murat
Recently, interfacial layer such as metal oxide, insulator and polymer have been used by scientists between the metal and semiconductor to increase the stability of the metal-semiconductor heterojunctions. These materials have been varied according to their usage aims. In this study, graphene nanoribbons (GNR) and 7,7,8,8 Tetracyanoquinodimethane (TCNQ, C12H4N4) layer has been used as interfacial layer between the metal and semiconductor for photodiode applications. The TCNQ layer collects and extracts more electrons in the interface of the device and is used as electron acceptor material for organic solar cells. Herein, we fabricated Al/p-Si/Al, Al/p-Si/TCNQ/Al and Al/p-Si/TCNQ:GNR/Al heterojunctions by physical vapor deposition technique. I-V measurements has been employed under dark and various light illumination conditions to show dielectric properties of the fabricated heterojunctions. From current-voltage characteristics, we calculated the electronic parameters such as ideality factor, barrier heights, series resistances and rise times. It can be concluded from overall results that TCNQ and TCNQ:GNR layers had a major impact on quality and can be considered as quite proper materials for optoelectronic applications.
Endemik Cousinia decolorans Freyn & Sint. (Asteraceae) Türünün Anatomik, Palinolojik ve Mikromorfolojik Özellikleri
(Selçuk Üniversitesi Fen Fakültesi, 2021) Ulukuş, Deniz; Atasagun, Bayram; Tugay, Osman
Cousinia (Asteraceae, Cardueae) cinsi çiçekli bitkiler içerisinde tür sayısı bakımından 50. büyük cins ve Asteraceae familyası içerisinde yaklaşık 700 türle temsil edilen en büyük cinslerden biridir. Bu çalışma, Cousinia seksiyonu içerisinde yer alan Cousinia decolorans türünün anatomik, palinolojik mikromorfolojik özelliklerinin belirlenerek cinsin sistematiğine katkı sağlamak amacıyla yapılmıştır. C. decolorans türünün polen mikromorfolojik özellikleri çalışılmış ve türe ait fotoğraflar verilmiştir. Bu türün anatomik çalışmasında gövde, yaprak ve orta damar özellikleri tespit edilerek fotoğrafları verilmiştir. Anatomik çalışmalar için bitki kısımları parafine gömülmüş ve dokuların boyanma işlemi için safranin fast green boyama metodu uygulanmıştır. Anatomik karakterlerden orta damar şeklinin yarıorbikular ve orta damardaki iletim demeti sayısının 3 olmasıyla bu karakterlerin türler arasında ayrımda kullanılabileceği belirlenmiştir. Palinolojik çalışmalarda ışık mikroskobu kullanılarak polen şeklinin prolat olduğu tespit edilmiştir. Polen ekzin yüzey süslerinin belirlenmesi için SEM mikroskobu kullanılıp, polenlerin fotoğrafları çekilmiş ve polen yüzeylerinin verrukat olduğu belirlenmiştir. Ayrıca akenlerin morfolojik ve mikromorfolojik özellikleri incelenmiş ve yüzey ornamentasyonunun retipilat olduğu belirlenmiştir.
Endemik Cousinia aucheri DC. (İnce Kızan) Üzerine Anatomik, Palinolojik ve Mikromorfolojik Araştırmalar
(Selçuk Üniversitesi Fen Fakültesi, 2021) Tugay, Osman; Atasagun, Bayram; Ulukuş, Deniz
Cousinia, Asteraceae’deki en büyük cinslerden biridir, Güneybatı ve Orta Asya’da 700 tür içermektedir. Cousinia seksiyonu Türkiye’de 23 tür ile temsil edilmektedir. Cousinia’nın taksonomisi tartışmalıdır. Anatomi ve polen morfolojisinin kullanılması, türlerin tanımlanması ve sınırlandırılması için faydalı bir araç olabilmektedir. Bu nedenle bu çalışmada Cousinia aucheri DC’nin anatomik, palinolojik ve aken mikromorfolojik özelliklerini araştırmayı ve Cousinia’nın sistematiğine katkı sağlamayı amaçladık. Anatomik çalışmalar için gövde, yaprak ve orta damar kesitlerinde parafin yöntemi kullanıldı. Palizat parankima sayısı, orta damarın şekli, damar demetlerinin sayısı ve düzenlenişinin önemli taksonomik bilgiler sağladığı belirlendi. Polen preparatları Wodehouse yöntemine göre hazırlandı. Polen taneleri trikolporat aperture ve verrukat süslemeye sahip olduğu belirlenmiştir. Ayrıca akenlerin morfolojik ve mikromorfolojik özellikleri araştırılmış ve yüzey süslemelerinin retipilat olduğu tespit edilmiştir.
Planktonlarda Siklomorfozis Üzerine Derleme
(Selçuk Üniversitesi Fen Fakültesi, 2018) Altındağ, Ahmet; Berdi̇, Duygu; Yıldıztugay, Evren; Küçüködük, Mustafa
Siklomorfizm veya mevsimsel polimorfizm zooplanktonlarda ilk olarak Lauterborn tarafından 1904 yılında tanımlanmıştır. Bu terim günümüzde küçük akuatik organizmalarda abiyotik (sıcaklık, türbülans, ıs?ık) ve biyotik (besin, predatör baskısı) çevrenin etkisiyle vücut yapılarında mevsimsel olarak meydana gelen fiziksel deg?is?iklikler olarak adlandırılmaktadır. Bu mevsimsel değişiklikler türün mevsimsel olarak iki farklı form gibi görünmesine neden olabilmektedir. Siklomorfosiz özellikle planktonik kladoseralar arasında daha fazla gözlemlenirken, ayrıca protozoa, dinoflagellat ve rotiferler arasında da yaygın olarak görülmektedir. Siklomorfosiz sonucu canlıların fiziksel görünüşlerinde ve davranışlarında birtakım değişiklikler söz konusudur. Siklomorfosiz akuatik ortamda organizmanın batma oranını azaltıp yüzmede kolaylık sag?larken, aynı zamanda planktonla beslenen predatörlere kars?ı da bir savunma mekanizması olarak kullanılmaktadır. Araştırmacılar tarafından bazı avcı türlerin salgıladığı kimyasalların (kairomonlar) canlıda kaudal spin, tepelik gibi vücut çıkıntılarına neden olduğu ortaya konmuştur. Bu derleme de planktonlardaki siklomorfosiz olayı ve meydana gelen değişikliklerden detaylı olarak bahsedilmiştir.
Hydrogen sulfide (H2S) and nitric oxide (NO) alleviate cobalt toxicity in wheat (Triticum aestivum L.) by modulating photosynthesis, chloroplastic redox and antioxidant capacity
(Elsevier B.V., 2020) Özfidan Konakçı, Ceyda; Yıldıztugay, Evren; Elbasan, Fevzi; Küçükoduk, Mustafa; Türkan, İsmail
The role of hydrogen sulfide (H2S)/nitric oxide (NO) in mitigating stress-induced damages has gained interest in the past few years. However, the protective mechanism H2S and/or NO has towards the chloroplast system through the regulation of redox status and activation of antioxidant capacity in cobalt-treated wheat remain largely unanswered. Triticum aestivum L. cv. Ekiz was treated with alone/in combination of a H2S donor (sodium hydrosulfide (NaHS,600?M)), a NO donor (sodium nitroprusside (SNP,100?M)) and a NO scavenger (rutin hydrate (RTN,50?M)) to assess how the donors affect growth, water relations, redox and antioxidant capacity in chloroplasts, under cobalt (Co) concentrations of 150-300 ?M. Stress decreased a number of parameters (growth, water content (RWC), osmotic potential (??), carbon assimilation rate, stomatal conductance, intercellular CO2 concentrations, transpiration rate and the transcript levels of rubisco, which subsequently disrupt the photosynthetic capacity). However, SNP/NaHS counteracted the negative effects of stress on these aforementioned parameters and RTN application with stress/non-stress was reversed these effects. Hydrogen peroxide (H2O2) and TBARS were induced under stress in spite of activated ascorbate peroxidase (APX). SNP/NaHS under stress increased activation of superoxide dismutase (SOD), peroxidase (POX), APX, glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), ascorbate (tAsA) and glutathione (GSH). In conclusion, NaHS/SNP are involved in the regulation and modification of growth, water content, rubisco activity and up-regulation of ascorbate-glutathione cycle (AsA-GSH) in chloroplast under stress. © 2020 Elsevier B.V.
Discovery of kynurenines containing oligopeptides as potent opioid receptor agonists
(MDPI AG, 2020) Szucs, Edina; Stefanucci, Azzurra; Dimmito, Marilisa Pia; Zádor, Ferenc; Pieretti, Stefano; Zengin, Gökhan; Vécsei, László
Kynurenine (kyn) and kynurenic acid (kyna) are well-defined metabolites of tryptophan catabolism collectively known as “kynurenines”, which exert regulatory functions in host-microbiome signaling, immune cell response, and neuronal excitability. Kynurenine containing peptides endowed with opioid receptor activity have been isolated from natural organisms; thus, in this work, novel opioid peptide analogs incorporating L-kynurenine (L-kyn) and kynurenic acid (kyna) in place of native amino acids have been designed and synthesized with the aim to investigate the biological effect of these modifications. The kyna-containing peptide (KA1) binds selectively the ?-opioid receptor with a Ki = 1.08 ± 0.26 (selectivity ratio ?/?/? = 1:514:10000), while the L-kyn-containing peptide (K6) shows a mixed binding affinity for ?, ?, and ?-opioid receptors, with efficacy and potency (Emax = 209.7 + 3.4%; LogEC50 = ?5.984 + 0.054) higher than those of the reference compound DAMGO. This novel oligopeptide exhibits a strong antinociceptive effect after i.c.v. and s.c. administrations in in vivo tests, according to good stability in human plasma (t1/2 = 47 min). © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
Chemical characterization, antioxidant, enzyme inhibitory and cytotoxic properties of two geophytes: Crocus pallasii and Cyclamen cilicium
(Elsevier Ltd, 2020) Zengin, Gökhan; Mahomoodally, Mohamad Fawzi; Sinan, K. I.; Picot-Allain, M. C. N.; Yıldıztugay, Evren; Cziáky, Z.; Jek?, J.
The Crocus and Cyclamen genus have been reported to possess diverse biological properties. In the present investigation, two geophytes from these genus, namely Crocus pallasi and Cyclamen cilicium have been studied. The in vitro antioxidant, enzyme inhibitory, and cytotoxic effects of the methanol extracts of Crocus pallasii and Cyclamen cilicium aerial and underground parts were investigated. Antioxidant abilities of the extracts were investigated via different antioxidant assays (metal chelating, radical quenching (ABTS and DPPH), reducing power (CUPRAC and FRAP) and phosphomolybdenum). Cholinesterases, amylase, tyrosinase, and glucosidase were used as target enzymes for detecting enzyme inhibitory abilities of the samples. Regarding the cytotoxic abilities, breast cancer cell lines (MDA-MB 231 and MCF-7) and prostate cancer cell lines (DU-145) were used. The flowers extracts of Crocus pallasii and C. cilicium possessed the highest flavonoid content. The highest phenolic content was recorded from C. cilicium root extract (47.62 mg gallic acid equivalent/g extract). Cyclamen cilicium root extract showed significantly (p < 0.05) high radical scavenging (94.28 and 139.60 mg trolox equivalent [TE]/g extract, against DPPH and ABTS radicals, respectively) and reducing potential (173.30 and 109.53 mg TE/g extract, against CUPRAC and FRAP, respectively). The best acetylcholinesterase, glucosidase and tyrosinase inhibition was observed in C. cilicium root (4.46 mg GALAE/g; 15.75 mmol ACAE/g; 136.99 mg KAE/g, respectively). Methanolic extracts of C. pallasii and C. cilicium showed toxicity against breast cancer cell lines. In light of the above findings, C. cilicium might be considered as an interesting candidate in the development of anti-cancer agent coupled with antioxidant properties. © 2020 Elsevier Ltd
Ternary CuCo2S4 thiospinel nanocrystal-coated photodiode with improved photoresponsivity and acceptance angles for optoelectronic applications
(SPRINGER, 2020) Yildirim, Murat.; Kocyigit, Adem.; Sarilmaz, Adem.; Ozel, Sultan Suleyman.; Kus, Mahmut.; Ozel, Faruk.
Ternary-structured thiospinels have attracted great attention in recent years for energy applications due to their attractive characteristics such as simple production, earth-abundant components and non-toxic nature. In this work, copper cobalt sulfide (CuCo2S4 or carrollite) thiospinel nanocrystals were synthesized by a hot-injection method, and detailed electrical and optoelectronic characterizations were performed in a Schottky device. The synthesized nanocrystals were used as an interfacial layer between the Au metal and p-Si semiconductor to obtain an Au/CuCo2S4/p-Si device. The structural and morphological characterizations confirmed the crystallinity, nanostructure and composition of the CuCo2S4 nanocrystals. The I-V and C-V measurements were employed to characterize the Au/CuCo2S4/p-Si device for various illumination intensities. The obtained device exhibited good rectifying and photodiode properties as well as good photocapacitance. The Au/CuCo2S4/p-Si device can be used and improved for optoelectronic applications.
Synthesis of novel tetrazine based D-pi-A organic dyes for photoelectrochemical and photocatalytic hydrogen evolution
(ELSEVIER SCIENCE SA, 2020) Aslan, Emre.; Karaman, Merve.; Yanalak, Gizem.; Bilgili, Hakan.; Can, Mustafa.; Ozel, Faruk.; Patir, Imren Hatay.
Two novel donor-pi-acceptor (D-pi-A) dyes, called as MK-2 and MK-8, are synthesized. Their structural, optical and electrochemical properties are investigated by NMR, absorption/photoluminescence spectroscopies and cyclic voltammetry techniques, respectively. Photocatalytic and photoelectrochemical hydrogen evolution properties of these D-pi-A dyes are explored by using triethanolamine (TEOA) as a sacrificial electron donor under anaerobic conditions and visible light irradiation with or without co-catalysts (Cu2WS4 and Pt) for the first time. Photoelectrochemical and photocatalytic hydrogen evolution reaction (HER) activities of these dyes are studied by using TiO2 coated FTO electrodes and powdered TiO2 (Degussa P25), respectively. Photoelectrochemical response of MK-2/TiO2 and MK-8/TiO2 are figured out in the order of 180 mu A cm(-1) and 80 A cm(-1). The photocatalytic hydrogen evolution amounts of MK-2/TiO2, MK-2/TiO2/Cu2WS4, MK-2/TiO2/Pt, MK-8/TiO2, MK-8/TiO2/Cu2WS4 and MK-8/TiO2/Pt are turned out to be 565, 920, 1828, 374, 522 and 1260 mu molg(-1) h(-1), respectively. Dye/TiO2 photocatalysts are displayed good stability in the both photochemical HER experiments. The alteration in the HER activities of MK-2 and MK-8 is explained by molecule structures of dyes. The proposed mechanism of photocatalytic hydrogen evolution is clarified by using electrochemical band levels of each constituent.
Morphology, anatomy and palynology of two endemic Cousinia cass. species (sect. Cousinia, Asteraceae) and their taxonomic implications
(PAKISTAN BOTANICAL SOC, 2020) Ulukuş, Deniz.; Tugay, Osman.
The morphological, anatomical and palynological features of Cousinia eleonorae Hub.-Mor. and Cousinia humilis Boiss. are provided along with their taxonomic significance. Their expanded description, distribution map and coloured photographs are also given. The morphological characteristics of leaves, phyllaries are taxonomically significant for distinguishing Cousinia species. In addition, the micromorphological characteristics of pollen grains and achenes are provided with the use of scanning electron microscopy. Anatomical characters such as number of cortex cells, number of vascular bundles and midrib shape are found to be significant characters. Moreover, exine sculpturing pattern and shape of pollen grains can be used for taxonomic purposes.
Green preparation of Carbon Quantum dots using Gingko biloba to sensitize TiO2 for the photohydrogen production
(ELSEVIER SCI LTD, 2020) Genc, Munevver Tuna.; Yanalak, Gizem.; Arslan, Gulsin.; Patir, Imren Hatay.
Carbon Quantum dots (CQDs) were obtained from Gingko biloba by using microwave technique, which is easy, time-saving, cost-effective, non-toxic and environmental friendly way. TiO2 were sensitized by green-prepared CQDs to obtain CQDs/TiO2 composite. The characterizations of the CQDs and CQDs/TiO2 were performed by Transmission Electron Microscopy (TEM), high-resolution TEM (HR-TEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopic (XPS), Photoluminescence (PL) and Fourier Transformed Infrared (FT-IR) spectroscopy. The photocatalytic hydrogen evolution activity of CQDs/TiO2 system was studied under visible light (lambda > 420 nm) irradiation in the aqueous solution by using triethanolamine (TEOA) as a sacrificial electron donor. When Pt was used as a co-catalyst, CQDs/TiO2/Pt exhibited improved hydrogen evolution rate (1502 mu mol h(-1)g(-1)) compared to CQDs/TiO2 composite (665 mu mol h(-1)g(-1)).
Assessment of antioxidant system and enzyme/nonenzyme regulation related to ascorbate-glutathione cycle in ferulic acid-treated Triticum aestivum L. roots under boron toxicity
(TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2020) Konakçı, Ceyda Özfidan; Yıldıztugay, Evren; Elbasan, Fevzi; Yıldıztugay, Ayşegül; Küçüködük, Mustafa
Ferulic acid (FA; 3-methoxy-4-hydroxycinnamic acid) can eliminate stress-induced damage because of its ability to induce antioxidant activity under stress. The aim of this study was to identify the effects of FA on water status, antioxidant system, and lipid peroxidation in wheat (Triticum aestivum L.) roots exposed to boron (B) stress. Plants were grown in hydroponic culture containing the combination or alone form of 25-75 mu M FA and 4-8 mM B. Stress significantly decreased growth (RGR), water content (RWC), proline content (Pro), and osmotic potential (psi(H)). However, FA alleviated the decrease in RGR, RWC, and Pro content. Compared to the control groups, stress decreased the activities of superoxide dismutase (SOD), peroxidase (POX), catalase, and ascorbate peroxidase (APX), but an increase was only observed in glutathione reductase (GR) activity. Hydrogen peroxide (H2O2) content accumulated with B stress. Besides, a notable decrease was observed in the scavenging activity of hydroxyl radical (OH center dot); thus, wheat roots had high lipid peroxidation (thiobarbituric acid reactive substance content). In response to stress, FA triggered the activities of SOD, POX, and APX. Moreover, when FA was made present in stressed wheat roots, we observed the enhanced activities of dehydroascorbate reductase, and monodehydroascorbate reductase and dehydroascorbate contents which are related to ascorbate-glutathione cycle, so FA could maintain ascorbate (AsA) regeneration. However, when wheat roots were treated with stress, FA did not induce the regeneration of glutathione because of decline in GR activity. Due to successful elimination of H2O2 content, the exogenous application of FA alleviated B-induced lipid peroxidation in wheat. Consequently, FA eliminated the damage induced by B stress via the increased POX and the enzymes related to Asada-Halliwell pathway (AsA-GSH cycle) in wheat roots.
Bazı Ruta L. ekstraktlarının biyoaktif madde içerikleri ve radikal kovucu aktiviteleri
(KAHRAMANMARAS SUTCU IMAM UNIV REKTORLUGU, 2019) Yaman, Cennet.; Ulukuş, Deniz.; Tugay, Osman.
Ruta L. is a genus of the Rutaceae family, mostly used as a traditional medicinal plant. In this study, the antioxidant activities of methanolic and ethanolic extracts of wild Ruta chalepensis L. (above ground plant) and Ruta montana L. (leaves-flowers, stems) were assessed. The results showed that methanol extract of flower-leave of Ruta montana provided the highest yield of extraction (15.11%, 151.12 +/- 0.78 mg/g) whereas the lowest yield was obtained in ethanol extract of stems of Ruta montana (2.67%, 26.66 +/- 0.50 mg/g). Total flavonoid content in dry weight of methanol and ethanol extracts of Ruta chalepensis was found higher than other extracts except methanol leaves-flowers extract of Ruta montana. It was determinated that ethanol extracts of Ruta montana stem sustained less total flavonoid and phenolic content. Also, radical scavenging activities such as 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and 2, 2'-Azino-Bis-3-Ethylbenzothiazoline-6-Sulfonic acid (ABTS) of extracts was investigated, and according to the solvent, it was revealed that extracts of Ruta chalepensis exhibited high activity. As a result, it has been discussed that Ruta can be used as a natural antioxidant by taking advantage of these data.
The synthesis of 4,4-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(N,N-diphenylaniline) organic semiconductor and use of it as an interlayer on Au/n-Si diode
(SPRINGER, 2019) Yıldırım, Murat; Erdoğan, Ayşenur; Yüksel, Ömer Faruk; Kuş, Mahmut; Can, Mustafa; Akın, Ü.; Tuğluoğlu, Nihat
In the present study, firstly, a 4,4-(9,9-dioctyl-9H-fluorene-2,7-diyl)bis(N,N-diphenylaniline) (FC) organic compound was synthesized and its structural and optical characterization were carried. Then, the effect on the device of the FC thin film prepared between n-type silicon substrate and gold metal by the spin coating technique was reported. The ideality factor (n), barrier height (phi B) and series resistance (Rs) values of the prepared structure from the I-V data have been found at 1.08, 0.78eV and 240 at room temperature (300K), respectively. According to the Gaussian distribution of the barrier height obtained from the various temperature ranges (220-380K), the phi b0 and A* values from the ordinate intercept and the slope of the modified Richardson curve of ln versus 1/T plot which has been found to be 0.97eV and 114 A/cm(2)K(2), respectively. Results indicate that the high barrier height is achieved for the Au/FC/n-Si metal-organic layer-semiconductor diode as compared to the Au/n-Si metal-semiconductor (MS) diode.
The investigation of novel D-pi-A type dyes (MK-3 and MK-4) for visible light driven photochemical hydrogen evolution
(ELSEVIER SCI LTD, 2019) Aslan, Emre.; Karaman, Merve.; Yanalak, Gizem.; Can, Mustafa.; Ozel, Faruk.; Patir, Imren Hatay.
Two novel donor-n-acceptor (D-pi-A) semiconductor organic dyes have been synthesized for the photochemical hydrogen evolution reaction (HER) to sensitize TiO2 for the first time. The molecular structures of D-pi-A semiconductor organic dyes, which are entitled as MK-3 and MK-4, have been characterized by NMR spectroscopy method; and also electrochemical and optical properties have been investigated by cyclic voltammetry and UV-Vis absorption techniques, respectively. Amount of dye loading on TiO2 surface has been investigated by EDX method. The HER activities have been explored in the presence of triethanolamine (TEOA) as a electron donor reagent under sunlight (solar simulator illumination limited by cut-off filter lambda >= 420 nm) in the absence and presence of co-catalysts (Pt and Cu2WS4). Transient photocurrent densities of MK-3/TiO2 and MK-4/TiO2 electrodes have been reached to 110 mu A cm(-1) and 275 mu A cm(-1), respectively. The photocatalytic HER activities have been relatively enhanced in the presence of the Pt or Cu2WS4 co-catalysts (dye/TiO2/Cu2WS4 or dye/TiO2/Pt) when compared to only dye/TiO2. The HER rates have been found as 427, 1277, 675, 682, 1027 and 795 mu molg(-1) h(-1) for the MK-3/TiO2, MK-3/TiO2 /Pt, MK-3/TiO2/Cu2WS4, MK-4/TiO2, MK-4/TiO2/Pt and MK4/TiO2/Cu2WS4 , respectively. The differences of photochemical activities of MK-3/TiO2 and MK-4/TiO2 have been stated taking into account dye molecule structures. Moreover, the HER mechanism have been described by using electrochemical band energy levels of dyes, TiO2 and Cu2WS4 co-catalyst.
The effect of the triangular and spherical shaped CuSbS2 structure on the electrical properties of Au/CuSbS2/p-Si photodiode
(SPRINGER, 2019) Yıldırım, Murat.; Kocyigit, Adem.; Sarılmaz, Adem.; Ozel, Faruk.
CuSbS2 (Chalcostibite) crystals were synthesized by the hot-injection method as triangular and spherical shaped structures. The crystals were inserted by spin coating technique as interfacial layers between Au metal and p-Si to investigate their electrical and photoresponse properties via I-V measurements under various light intensities. The XRD measurements were performed to show the crystalline structure of the spherical and triangular CuSbS2. The TEM images confirmed the triangular and spherical particle structures of the CuSbS2 crystals. The I-V measurements were performed under dark, 20-100mW light intensities with 20mW interval for spherical and triangular CuSbS2 photodiodes. In addition, diode parameters were extracted and discussed in the details. The results highlighted that triangular and spherical shaped structures have good photoresponse to the illumination and can be employed in the photodiode and photodetector applications.
The effect of indium doping concentration on the electrical and dielectric properties of Al/In:ZnO/p-Si heterojunctions
(ELSEVIER, 2019) Yıldırım, M.; Erdal, M. O.; Kocyigit, A.
Undoped and 0.1% 0.5% and 1.0% indium doped ZnO thin films were obtained by spin coating method as interfacial thin film layer between Al metal and p-Si semiconductor to investigate dielectric properties of the Al/In: ZnO/p-Si heterojunctions. Impedance spectroscopy technique was employed to characterize the dielectric properties of the Al/In: ZnO/p-Si heterojunctions depending on frequency (from 10 kHz to 1 MHz) and voltage (from - 5 V to + 5 V). The results imparted that interface states (N-ss), series resistance (R-s), barrier height (Phi(b)) and the concentration of acceptor atoms (N-a) influenced frequency changes. The dielectric parameters such as dielectric constant (epsilon'), dielectric loss (epsilon ''), loss tangent (tan delta), real and imaginary parts of the electric modulus (M' and M '') and ac electrical conductivity (sigma) values were calculated from impedance spectroscopy measurements and discussed in details for changing frequency and voltage for various In doped ZnO thin film interlayers. The dielectric properties of the Al/In:ZnO/p-Si heterojunctions were affected both In doping concentration and the frequency and voltage changes. The Al/In:ZnO/p-Si heterojunctions can be considered for industrial applications to increase the control.
The C-V characteristics of the Cu2WSe4/p-Si heterojunction depending on wide range temperature
(SPRINGER, 2019) Koçyiğit, Adem.; Küçükçelebi, Hayreddin.; Sarılmaz, Adem.; Ozel, Faruk.; Yıldırım, Murat.
Cu2WSe4 nanosheets were synthesized by hot-injection method and employed as interfacial layers between the p-Si and Au metal via spin coating technique. The capacitance-voltage (C-V) and conductance-voltage (G-V) measurements were performed on the Cu2WSe4/p-Si heterojunction device depending on wide range temperatures from 80 to 400K by 40 K steps. The device exhibited decreasing capacitance behavior with increasing temperature at the inversion region because of the interface states and series resistance. The conductance values increased with increasing temperature owing to increasing free charge carriers. The series resistance (R-s) and interface states density (N-ss) were extracted from C-V and G-V measurements and discussed in the details. The results highlighted that the electrical parameters are a strong function of the voltage and temperature. The Au/Cu2WSe4/p-Si device can be employed for controllable capacitor applications.
The Au/Cu2WSe4/p-Si photodiode: Electrical and morphological characterization
(ELSEVIER SCIENCE SA, 2019) Kocyigit, Adem.; Yıldırım, Murat.; Sarılmaz, Adem.; Ozel, Faruk.
Cu2WSe4 nanosheets were synthesized by the hot-injection method and put as interfacial layers between Au metal and p-Si by spin coating technique to investigate their photoresponse and capacitor properties via I-V and C-V measurements, respectively. The XRD were operated to confirm crystalline structure of the Cu2WSe4. The TEM image revealed that the crystalline nanosheet structures of the Cu2WSe4. The I-V measurements were performed under dark and light illumination in the range 20 mW-100 mW light intensities with 20 mW interval. In addition, some diode parameters such as ideality factor, barrier height and series resistance were extracted via a various method and discussed in the details. The C-V measurements were employed for various frequency and voltages. The C-V characteristics of the device confirmed the strong dependence on the frequency and voltage. The results imparted that Au/Cu2WSe4/p-Si can be employed for photodiode, photodetector and capacitor applications. (C) 2018 Elsevier B.V. All rights reserved.
Temperature dependent current-voltage characteristics of Al/TiO2/n-Si and Al/Cu:TiO2/n-Si devices
(ELSEVIER SCI LTD, 2019) Erdal, Mehmet Okan.; Kocyigit, Adem.; Yıldırım, Murat.
We fabricated undoped and Cu doped TiO2 thin films by spin coating technique and employed the films as interfacial oxide layer between the Al and n-type Si to investigate the effect of temperature on the Al/TiO2/n-Si and Al/Cu:TiO2/n-Si devices. For that aim, the I-V measurements were performed in the range of 50 K-400 K by 50 K interval. The devices exhibited good rectifying behavior and thermal response in a wide range temperature. Ideality factor, barrier height and series resistance were calculated from I-V measurements for various temperatures by thermionic emission theory, Norde and Cheung methods and discussed in the details. The obtained results revealed that the device parameters are a strong function of the temperature. The interface states (N-ss) were affected by the changing of the temperatures. The Al/TiO2/n-Si and Al/Cu:TiO2/n-Si devices can be performed for wide range temperatures in various technological applications.

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